1. Field of the Invention
The present invention relates to a spiral inductor, and more particularly, to a spiral inductor provided to an integrated circuit (IC) of a variety of communication devices using a high frequency band, wherein a metal line of the spiral conductor is embodied as conductors having different widths and open or short-type stubs are formed at one side of each of the conductors to induce parasitic capacitances or inductances. A whole inductance value of the spiral inductor can be controlled accurately depending on use purpose by selectively connecting conductors having different widths through switching means.
2. Description of the Prior Art
FIG. 1 is a perspective view showing an example of a conventional spiral inductor. As shown, the inductor comprises a first port 10, a second port 11 and a Via contact 12.
The first and second ports 10, 11 are terminals through which a signal is inputted and outputted and are arranged to be spaced perpendicularly to an insulating film, which is a silicone substrate, thereby forming a structure connected to each other by the via contact 12 passing through the insulating film. In the structure, the second port 11 is spirally turned toward a center thereof from an outer periphery.
In case of the spiral conductor as described above, since there is no mutual inductance between the first and second ports 10, 11, it is required to change number, shape and size of the second port 11, thereby varying turns of the spiral, an inner diameter, a width of the metal line, a distance between the metal lines and the like, so as to increase a whole inductance.
However, in this case, the whole inductance is also increased, thereby decreasing a degree of integration in an entire circuit. In addition, when an area of the inductor is increased to a predetermined size or more, a parasitic capacitance, which occurs between the respective ports 10, 11 and the substrate, is also increased, so that a quality factor (Q-factor) of the inductor is rapidly decreased and the whole inductance is not increased any more.
Further, the maximum Q-factor of the inductor is generated in only a specific frequency, so that it is impossible to generate the maximum Q-factor in a frequency band that a circuit designer desires.